1. Field of the Invention
The present invention relates to a substrate module mounted with a heat generating device such as a light emitting diode and a power chip, and more particularly, to an anodized metal substrate module superior in heat radiation properties, which can be applied to a backlight unit and a surface light source device.
2. Description of the Related Art
Recently, researches have been under way to improve heat radiation properties of a circuit board. Conventionally, a heat generating device has been mounted on a printed circuit board (PCB) having an insulating base substrate. However, a typical PCB, if mounted with a device such as a light emitting diode or a power chip which generates a considerable amount of heat, is degraded in reliability due to poor heat transfer properties thereof. The typical PCB with inferior heat radiation properties proves disadvantageous for a backlight unit of a liquid crystal display (LCD) or a surface light source device.
FIG. 1 is a schematic cross-sectional view illustrating a conventional printed circuit board (PCB). Referring to FIG. 1, the PCB 10 includes an insulating base substrate 11 made of resin or plastic and upper and lower conductive lines 14 formed on and underneath the base substrate 11, respectively. The upper and lower conductive lines 14 can be electrically connected with each other by, for example, a conductive via. In addition to this function of electrical connection, the via 15 may serve as a heat transfer path. Components (e.g., an LED or power chip) are mounted on the base substrate 11 to be connected to the conductive lines 14.
This conventional PCB 10 is relatively inexpensive due to low-cost materials and easy processability. But the PCB 10 is poor in heat radiation properties due to its high heat resistance. In an effort to overcome this problem, a metal core PCB (MCPCB) adopting a metal member with superb heat transfer properties has been proposed. FIG. 2 is a schematic cross-sectional view illustrating the MCPCB. Referring to FIG. 2, the MCPCB 20 includes a metal core substrate 21 made of Al and a polymer insulating layer 23 formed thereon. Conductive lines 25 are formed on the polymer insulating layer 23 and necessary devices 27 and 28 are mounted on the polymer insulating layer 23. This MCPCB 20 exhibits superior heat radiation properties to the conventional PCB (see FIG. 1). Yet the MCPCB 20 adopts the high-cost polymer insulating layer 23 with relatively high thermal conductivity, thereby considerably increasing manufacturing costs thereof.